This invention relates generally to an automation and welding control system and more particularly to a computerized automation and welding control system wherein the welding control system is capable of controlling a large number of welding heads from a single computer, the computer providing control of the timing for the various portions of the welding cycle.
In prior welding systems, it has been typical to provide a welding control unit for each welding head, the welding control unit being located proximate the welding head. In factories having a low number of welding heads, such a system may be feasible and economical. However, if a manufacturing plant requires a large number of welding heads, for example a hundred heads or more, it has been found that the welding system can be more favorably controlled, maintained and operated by providing a central welding control center which includes a computerized control of the various portions of the welding cycle.
With the system of the present invention, a single control can be provided for many types of welding operations, as for example seam welding, spot welding, arc welding, resistance welding, and other types. Further, the system provides a provision for monitoring the KVA demand on the entire welding system relative to the available KVA and controls the application of welding energy to the various welding heads in accordance with the available KVA so that the KVA being used does not fall below a certain level.
The welding system of the present invention is coordinated with an automation system wherein various functions and operations along an automated line are monitored and the data fed to the computer for storage therein and for use in generating control signals. The automation unit also includes a diagnostic terminal which permits the feeding of information from the floor to the computer and then to the diagnostic terminal for use by the operator of the line.
The details of the system of the present invention include the diagnostic terminal which permits communication with the computer through a hard-wire cable and a small interface. Any number of terminals may be connected to a computer controlled production line on a party line basis. However, this system is contemplated only to service one diagnostic terminal in any given instance.
The automation system comprises an appropriate number of automation satellites that connect to the welding stations and their associated transfer line. These satellites monitor the limit switches and other sensors on the machine and report their status via relatively inexpensive cable to the control master. The control master determines the intent of the inputs and causes outputs to permit the production line to continue the manufacturing process. In evolving the automation system, the various input and output printed circuit boards have been designated to be relatively simple and interchangable one with the other to permit ease in maintaining the facility and permit ready repair of the system without requiring a large number of printed circuit boards to be maintained in stock.
In the system of the present invention, a centralized computer master is mounted in a location which permits ease of monitoring of all of the welding heads and the automation line. The centralized master includes an interface unit for the computer and various input and output printed circuit cards which are utilized to provide data to and from the computer and also to control the flow of data to and from the computer. The master unit also includes the welding control cards, the power supply and a terminal rack to terminate the various connections to the master.
The master terminal also includes various input and output terminal devices such as a teletype writer unit, a cathode ray tube unit, a magnetic tape unit, a paper tape unit and a magnetic storage disk.
The portion of the system mounted on the floor includes, generally, an automation satellite, a power satellite, a weld-data input/output terminal, a diagnostic terminal and the various printed circuit boards required to control the welding operation. The automation satellite includes sensing circuits for sensing the closure of limit switches, contacts and other functions of that type and also provides triac output cards which are capable of controlling unit on the floor. The power satellite includes circuits to balance the load across the three phases feeding the various welding units and the contacts required to protect the power supply from any malfunction in the external circuits.
The controls for the welding guns includes a heat control circuit which is capable of controlling the percent heat between twenty and a hundred percent. Also, the heat control includes a false weld and weld override feature which is utilized to protect the system against malfunctioning in the welding portion of the welding cycle. The welding control circuit also includes a pilot and valve system which is utilized to turn on the valve and close the various pilots associated with a welding machine or gun. The welding control further includes a retract circuit which permits retracting of the welding gun beyond the normal opening of the jaws.
As will be seen from the following description of the invention, the automated system which comprises the basis of the present invention permits the precise control of a large number of welding guns while maintaining the quality of the welds to a degree beyond that which has been heretofore known in welding systems of the type including individual controls. Further, it has been found that, beyond a predetermined number of welding heads, it is more economical to centrally control the welding guns or machines with a central control module mounted in a remote room which may be maintained with ease and may be provided with an environment for the personnel operating the central control which is clean, free of noise and otherwise free of the hazards of a manufacturing operation.